Yi Xin Zeng

MicroRNA miR-21 overexpression in human breast cancer is associated with advanced clinical stage, lymph node metastasis and patient poor prognosis

To investigate the global expression profile of miRNAs in primary breast cancer (BC) and normal adjacent tumor tissues (NATs) and its potential relevance to clinicopathological characteristics and patient survival, the genome-wide expression profiling of miRNAs in BC was investigated using a microarray containing 435 mature human miRNA oligonucleotide probes. Nine miRNAs of hsa-miR-21, hsa-miR-365, hsa-miR-181b, hsa-let-7f, hsa-miR-155, hsa-miR-29b, hsa-miR-181d, hsa-miR-98, and hsa-miR-29c were observed to be up-regulated greater than twofold in BC compared with NAT, whereas seven miRNAs of hsa-miR-497, hsa-miR-31, hsa-miR-355, hsa-miR-320, rno-mir-140, hsa-miR-127 and hsa-miR-30a-3p were observed to be down-regulated greater than twofold. The most significantly up-regulated miRNAs, hsa-mir-21 (miR-21), was quantitatively analyzed by TaqMan real-time PCR in 113 BC tumors. Interestingly, among the 113 BC cases, high level expression of miR-21 was significantly correlated with advanced clinical stage (P = 0.006, Fishers exact text), lymph node metastasis (P = 0.007, Fishers exact text), and shortened survival of the patients (hazard ratio [HR]=5.476, P < 0.001). Multivariate Cox regression analysis revealed this prognostic impact (HR=4.133, P = 0.001) to be independent of disease stage (HR=2.226, P = 0.013) and histological grade (HR=3.681, P = 0.033). This study could identify the differentiated miRNAs expression profile in BC and reveal that miR-21 overexpression was correlated with specific breast cancer biopathologic features, such as advanced tumor stage, lymph node metastasis, and poor survival of the patients, indicating that miR-21 may serve as a molecular prognostic marker for BC and disease progression.

Bmi-1 Is a Novel Molecular Marker of Nasopharyngeal Carcinoma Progression and Immortalizes Primary Human Nasopharyngeal Epithelial Cells

The Bmi-1 oncoprotein regulates proliferation and oncogenesis in human cells. Its overexpression leads to senescence bypass in human fibroblasts and immortalization of human mammary epithelial cells. In this study, we report that compared with normal nasopharyngeal epithelial cells (NPEC), Bmi-1 is overexpressed in nasopharyngeal carcinoma cell lines. Importantly, Bmi-1 was also found to be overexpressed in 29 of 75 nasopharyngeal carcinoma tumors (38.7%) by immunohistochemical analysis. In contrast to nasopharyngeal carcinoma, there was no detectable expression of Bmi-1 in noncancerous nasopharyngeal epithelium. Moreover, high Bmi-1 expression positively correlated with poor prognosis of nasopharyngeal carcinoma patients. We also report that the overexpression of Bmi-1 leads to bypass of senescence and immortalization of NPECs, which normally express p16(INK4a) and exhibit finite replicative life span. Overexpression of Bmi-1 in NPECs led to the induction of human telomerase reverse transcriptase activity and reduction of p16(INK4a) expression. Mutational analysis of Bmi-1 showed that both RING finger and helix-turn-helix domains of it are required for immortalization of NPECs. Our findings suggest that Bmi-1 plays an important role in the development and progression of nasopharyngeal carcinoma, and that Bmi-1 is a valuable marker for assessing the prognosis of nasopharyngeal carcinoma patients. Furthermore, this study provides the first cellular proto-oncogene immortalized nasopharyngeal epithelial cell line, which may serve as a cell model system for studying the mechanisms involved in the tumorigenesis of nasopharyngeal carcinoma.

The polycomb group protein Bmi-1 represses the tumor suppressor PTEN and induces epithelial-mesenchymal transition in human nasopharyngeal epithelial cells

The polycomb group protein B lymphoma Mo-MLV insertion region 1 homolog (Bmi-1) is dysregulated in various cancers, and its upregulation strongly correlates with an invasive phenotype and poor prognosis in patients with nasopharyngeal carcinomas. However, the underlying mechanism of Bmi-1-mediated invasiveness remains unknown. In the current study, we found that upregulation of Bmi-1 induced epithelial-mesenchymal transition (EMT) and enhanced the motility and invasiveness of human nasopharyngeal epithelial cells, whereas silencing endogenous Bmi-1 expression reversed EMT and reduced motility. Furthermore, upregulation of Bmi-1 led to the stabilization of Snail, a transcriptional repressor associated with EMT, via modulation of PI3K/Akt/GSK-3beta signaling. Chromatin immunoprecipitation assays revealed that Bmi-1 transcriptionally downregulated expression of the tumor suppressor PTEN in tumor cells through direct association with the PTEN locus. This in vitro analysis was consistent with the statistical inverse correlation detected between Bmi-1 and PTEN expression in a cohort of human nasopharyngeal carcinoma biopsies. Moreover, ablation of PTEN expression partially rescued the migratory/invasive phenotype of Bmi-1-silenced cells, indicating that PTEN might be a major mediator of Bmi-1-induced EMT. Our results provide functional and mechanistic links between the oncoprotein Bmi-1 and the tumor suppressor PTEN in the development and progression of cancer.

A genome-wide association study of nasopharyngeal carcinoma identifies three new susceptibility loci

To identify genetic susceptibility loci for nasopharyngeal carcinoma (NPC), a genome-wide association study was performed using 464,328 autosomal SNPs in 1,583 NPC affected individuals (cases) and 1,894 controls of southern Chinese descent. The top 49 SNPs from the genome-wide association study were genotyped in 3,507 cases and 3,063 controls of southern Chinese descent from Guangdong and Guangxi. The seven supportive SNPs were further confirmed by transmission disequilibrium test analysis in 279 trios from Guangdong. We identified three new susceptibility loci, TNFRSF19 on 13q12 (rs9510787, Pcombined = 1.53 × 10−9, odds ratio (OR) = 1.20), MDS1-EVI1 on 3q26 (rs6774494, Pcombined = 1.34 × 10−8, OR = 0.84) and the CDKN2A-CDKN2B gene cluster on 9p21 (rs1412829, Pcombined = 4.84 × 10−7, OR = 0.78). Furthermore, we confirmed the role of HLA by revealing independent associations at rs2860580 (Pcombined = 4.88 × 10−67, OR = 0.58), rs2894207 (Pcombined = 3.42 × 10−33, OR = 0.61) and rs28421666 (Pcombined = 2.49 × 10−18, OR = 0.67). Our findings provide new insights into the pathogenesis of NPC by highlighting the involvement of pathways related to TNFRSF19 and MDS1-EVI1 in addition to HLA molecules.

The putative tumour suppressor microRNA-124 modulates hepatocellular carcinoma cell aggressiveness by repressing ROCK2 and EZH2

Background Recent profile studies of microRNA (miRNA) expression have documented a deregulation of miRNA (miR-124) in hepatocellular carcinoma (HCC). Objective To determine the status of miR-124 expression and its underlying mechanisms in the pathogenesis of HCC. Methods The expression levels of miR-124 were first examined in HCC cell lines and tumour tissues by real-time PCR. The in vitro and in vivo functional effect of miR-124 was examined further. A luciferase reporter assay was conducted to confirm target associations. Results The expression levels of miR-124 were frequently reduced in HCC cells and tissues, and low-level expression of miR-124 was significantly associated with a more aggressive and/or poor prognostic phenotype of patients with HCC (p<0.05). In HCC cell lines, stable overexpression of miR-124 was sufficient to inhibit cell motility and invasion in vitro, and suppress intrahepatic and pulmonary metastasis in vivo. In addition, ectopic overexpression of miR-124 in HCC cells inhibited epithelial–mesenchymal cell transition, formation of stress fibres, filopodia and lamellipodia. Further studies showed that miR-124 could directly target the 3′-untranslated region (3′-UTR) of both ROCK2 and EZH2 mRNAs, and suppress their mRNA and protein expressions. These findings suggest that miR-124 plays a critical role in regulating cytoskeletal events and epithelial–mesenchymal cell transition and, ultimately, inhibits the invasive and/or metastatic potential of HCC, probably by its direct target on ROCK2 and EZH2 genes. These results provide functional and mechanistic links between the tumour suppressor miRNA-124 and the two oncogenes ROCK2 and EZH2 on the aggressive nature of HCC. Conclusion These data highlight an important role for miR-124 in the regulation of invasion and metastasis in the molecular aetiology of HCC, and suggest a potential application of miR-124 in prognosis prediction and cancer treatment.

Genome-wide association study identifies 1p36.22 as a new susceptibility locus for hepatocellular carcinoma in chronic hepatitis B virus carriers

To identify susceptibility variants for hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC), we conducted a genome-wide association study by genotyping 440,794 SNPs in 355 chronic HBV carriers with HCC and 360 chronic HBV carriers without HCC, all of Chinese ancestry. We identified one intronic SNP (rs17401966) in KIF1B on chromosome 1p36.22 that was highly associated with HBV-related HCC and confirmed this association in five additional independent samples, consisting of 1,962 individuals with HCC, 1,430 control subjects and 159 family trios. Across the six studies, the association with rs17401966 was highly statistically significant (joint odds ratio = 0.61, P = 1.7 × 10−18). In addition to KIF1B, the association region tagged two other plausible causative genes, UBE4B and PGD. Our findings provide evidence that the 1p36.22 locus confers susceptibility to HBV-related HCC, and suggest that KIF1B-, UBE4B- or PGD-related pathways might be involved in the pathogenesis of this malignancy.

Genome-wide scan for familial nasopharyngeal carcinoma reveals evidence of linkage to chromosome 4.

Nasopharyngeal carcinoma (NPC) occurs with high frequency in Asian populations, especially among people of Cantonese ancestry. In areas with high incidence, NPC clusters in families, which suggests that both geography and genetics may influence disease risk. Although the HLA-Bw46 locus is associated with increased risk of NPC, no predisposing genes have been identified so far. Here we report the results of a genome-wide search carried out in families at high risk of NPC from Guangdong Province, China. Parametric analyses provide evidence of linkage to the D4S405 marker on chromosome 4 with a logarithm of odds for linkage (lod) score of 3.06 and a heterogeneity-adjusted lod (hlod) score of 3.21. Fine mapping with additional markers flanking D4S405 resulted in a lod score of 3.54 and hlod score of 3.67 for the region 4p15.1–q12. Multipoint nonparametric linkage analysis gives lod scores of 3.54 at D4S405 (P = 5.4 × 10−5) and 4.2 at D4S3002 (P = 1.1 × 10−5), which is positioned 4.5 cM away from D4S405. When Epstein–Barr virus antibody titer was included as a covariate, the lod scores reached 4.70 (P = 2.0 × 10−5) and 5.36 (P = 4.36 × 10−6) for D4S405 and D4S3002, respectively. Our findings provide evidence of a major susceptibility locus for NPC on chromosome 4 in a subset of families.

miR-125b is Methylated and Functions as A Tumor Suppressor by Regulating the ETS1 proto-oncogene in Human Invasive Breast Cancer

The microRNA miR-125b is dysregulated in various human cancers but its underlying mechanisms of action are poorly understood. Here, we report that miR-125b is downregulated in invasive breast cancers where it predicts poor patient survival. Hypermethylation of the miR-125b promoter partially accounted for reduction of miR-125b expression in human breast cancer. Ectopic restoration of miR-125b expression in breast cancer cells suppressed proliferation, induced G(1) cell-cycle arrest in vitro, and inhibited tumorigenesis in vivo. We identified the ETS1 gene as a novel direct target of miR-125b. siRNA-mediated ETS1 knockdown phenocopied the effect of miR-125b in breast cell lines and ETS1 overexpression in invasive breast cancer tissues also correlated with poor patient prognosis. Taken together, our findings point to an important role for miR-125b in the molecular etiology of invasive breast cancer, and they suggest miR-125b as a potential theranostic tool in this disease.

Identification of genetic susceptibility loci for colorectal tumors in a genome-wide meta-analysis

BACKGROUND & AIMS Heritable factors contribute to the development of colorectal cancer. Identifying the genetic loci associated with colorectal tumor formation could elucidate the mechanisms of pathogenesis. METHODS We conducted a genome-wide association study that included 14 studies, 12,696 cases of colorectal tumors (11,870 cancer, 826 adenoma), and 15,113 controls of European descent. The 10 most statistically significant, previously unreported findings were followed up in 6 studies; these included 3056 colorectal tumor cases (2098 cancer, 958 adenoma) and 6658 controls of European and Asian descent. RESULTS Based on the combined analysis, we identified a locus that reached the conventional genome-wide significance level at less than 5.0 × 10(-8): an intergenic region on chromosome 2q32.3, close to nucleic acid binding protein 1 (most significant single nucleotide polymorphism: rs11903757; odds ratio [OR], 1.15 per risk allele; P = 3.7 × 10(-8)). We also found evidence for 3 additional loci with P values less than 5.0 × 10(-7): a locus within the laminin gamma 1 gene on chromosome 1q25.3 (rs10911251; OR, 1.10 per risk allele; P = 9.5 × 10(-8)), a locus within the cyclin D2 gene on chromosome 12p13.32 (rs3217810 per risk allele; OR, 0.84; P = 5.9 × 10(-8)), and a locus in the T-box 3 gene on chromosome 12q24.21 (rs59336; OR, 0.91 per risk allele; P = 3.7 × 10(-7)). CONCLUSIONS In a large genome-wide association study, we associated polymorphisms close to nucleic acid binding protein 1 (which encodes a DNA-binding protein involved in DNA repair) with colorectal tumor risk. We also provided evidence for an association between colorectal tumor risk and polymorphisms in laminin gamma 1 (this is the second gene in the laminin family to be associated with colorectal cancers), cyclin D2 (which encodes for cyclin D2), and T-box 3 (which encodes a T-box transcription factor and is a target of Wnt signaling to β-catenin). The roles of these genes and their products in cancer pathogenesis warrant further investigation.

Trends in incidence and mortality of nasopharyngeal carcinoma over a 20–25 year period (1978/1983–2002) in Sihui and Cangwu counties in southern China

BackgroundNasopharyngeal carcinoma (NPC) is a rare malignancy in most parts of the world but is common in southern China. A recent report from the Hong Kong Cancer Registry, a high-risk area for NPC in southern China, showed that incidence rate decreased by 29% for males and by 30% for females from 1980–1999, while mortality rate decreased by 43% for males and 50% for females. Changing environmental risk factors and improvements in diagnosis and treatment were speculated to be the major factors contributing to the downward trend of the incidence and mortality rates of NPC. To investigate the secular trends in different Cantonese populations with different socio-economic backgrounds and lifestyles, we report the incidences and mortality rates from two population-based cancer registries in Sihui and Cangwu counties from 1978–2002.MethodsIncidence and mortality rates were aggregated by 5-year age groups and 5 calendar years. To adjust for the effect of difference in age composition for different periods, the total and age-specific rates of NPC incidence and mortality rate were adjusted by direct standardization according to the World Standard Population (1960). The Estimated Annual Percentage Change (EAPC) was used as an estimate of the trend.ResultsThe incidence rate of NPC has remained stable during the recent two decades in Sihui and in females in Cangwu, with a slight increase observed in males in Cangwu from 17.81 to 19.76 per 100,000. The incidence rate in Sihui is 1.4–2.0 times higher during the corresponding years than in Cangwu, even though the residents of both areas are of Cantonese ethnicity. A progressive decline in mortality rate was observed in females only in Sihui, with an average reduction of 6.3% (p = 0.016) per five-year period.ConclusionTo summarize, there is great potential to work in the area of NPC prevention and treatment in southern China to decrease NPC risk and improve survival risk rates in order to reduce M:I ratios. Future efforts on effective prevention, early detection and treatment strategies were also discussed in this paper. Furthermore, the data quality and completeness also need to be improved.